The local Health Department conducted a study in 2009 of 900 adults asking each adult the number of times they wash their hands per day. The mean number of times those sampled washed their hands was 7.946 with a standard deviation of 6.567. Researchers would like to include a 90% confidence interval. How many degrees of freedom would be associated with this t-distribution? With 90% confidence, we estimate the mean number of times an individual washes their hands is between and . Enter the lower limit in the first box and the upper limit in the second box. (The appropriate t critical point is t=1.65. Round the limits of your interval to 4 decimal places.)
The local Health Department conducted a study in 2009 of 900 adults asking each adult the number of times they wash their hands per day. The
- How many degrees of freedom would be associated with this t-distribution?
- With 90% confidence, we estimate the mean number of times an individual washes their hands is between and . Enter the lower limit in the first box and the upper limit in the second box. (The appropriate t critical point is t=1.65. Round the limits of your interval to 4 decimal places.)
- Based on the interval computed, can we conclude that the mean number of times local adults wash their hands is more than 8 times per day
Given Information:
Sample size (n) = 900
Sample mean () = 7.946
Standard deviation = 6.567
Degrees of freedom = 899
To construct 90% Confidence Interval for population mean:
Confidence Interval is obtained using the formula:
where, t* is the t-critical value at 90% Confidence Interval and degrees of freedom 899.
s is the standard deviation.
Since, sample size n is greater than 30 t* values are closer to Z-critical values.
t* = 1.65 (given)
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